1. Field of the Invention
The present invention relates to a surgical microscope apparatus used in an opthalmological surgery, and particularly relates to a surgical microscope apparatus comprising a head lens that focuses illumination light to illuminate the interior of an eye.
2. Description of the Related Art
In a conventional vitreoretinal surgery in the opthalmology field, the interior of an eye is observed by placing a surgical contact lens on the cornea and inserting a light guide (an optical fiber) into the interior of the eye to illuminate a surgical site. In this method, an operator holds the light guide in one hand and a surgical instrument in the other hand. Therefore, there has been such a problem that it is hard to perform a precise operation.
To solve this problem, a surgical microscope apparatus comprising a lens (a head lens) between an eye and an objective lens has been proposed (refer to Japanese unexamined patent application publication JP-A 2003-62003, for example). The head lens acts so as to focus illumination light passed through the objective lens and guide it to the interior of the eye. In practical use, a plurality of head lenses having different refractive powers are provided. These head lenses are selectively used depending on positions to observe the fundus oculi, etc.
An example of a surgical microscope apparatus having a head lens is shown in FIG. 15 and FIG. 16. A surgical microscope apparatus 100 is used to observe an eye E in a surgery of the fundus oculi (retina) Er, cornea Ec, crystalline lens El, etc.
One end of a first arm 3 is connected to the upper end of a supporting post 2 of the surgical microscope apparatus 100. One end of a second arm 4 is connected to the other end of the first arm 3. A drive unit 5 is connected to the other end of the second arm 4. An operator's microscope 6 is suspended from the drive unit 5. An assistant's microscope 7 is disposed together with the operator's microscope 6.
The surgical microscope apparatus 100 is provided with a foot switch 8. The operator operates the surgical microscope apparatus 100 by operating the foot switch 8 with his/her foot. The drive unit 5 vertically and horizontally moves the operator's microscope 6 and the assistant's microscope 7 in response to the operation by the foot switch 8, etc.
Various types of optical systems and drive systems are housed in a lens barrel part 10 of the operator's microscope 6. An inverter part 12 is disposed at the upper part of the lens barrel part 10. The inverter part 12 is an optical unit that converts an observation image obtained as a reverted image into an erected image. Right and left eye pieces 11L and 11R are disposed at the upper part of the inverter part 12.
Moreover, the upper edge of a holding arm 14 is connected to the operator's microscope 6. A head lens 13 is held at the lower edge of the holding arm 14. The upper edge of the holding arm 14 is pivotally disposed so that the holding arm 14 is rotatable in the vertical direction. Consequently, it is possible to insert the head lens 13 into a position between the eye E and an objective lens 15, and retract it from the position. The head lens 13 and the holding arm 14 are housed in a housing part, which is not shown in the drawings.
An optical system shown in FIG. 16 is housed in the lens barrel part 10 of the operator's microscope 6. FIG. 16 is a side view of the optical system seen from the side of the assistant's microscope 7. This optical system includes an illumination optical system 20 and observation optical systems 30.
The observation optical systems 30 are disposed on the respective sides of an optical axis O of the objective lens 15. Each of the observation optical systems 30 includes a zoom lens system 31, a beam splitter 32, an imaging lens 33, an image-erecting prism 34, an interpupillary adjusting prism 35, a field diaphragm 36, and an eyepiece 37.
The zoom lens system 31 is composed of a plurality of zoom lenses 31a, 31b and 31c. The beam splitter 32 separates part of light coming from the eye E, and guides it to the assistant's microscope 7 or a TV camera (not shown).
The illumination optical system 20 includes an illumination light source 21, a condenser lens 22, an illumination field diaphragm 23, a slit plate 24, an illumination prism 25, and a collimator lens 27.
A slit hole 24a is formed on the slit plate 24. Moreover, the slit plate 24 can be inserted into and retracted from an illumination light path of the illumination optical system 20. When being inserted in the illumination light path, the slit plate 24 can be moved in a direction orthogonal to an illumination optical axis O′. The slit hole 24a is formed in a direction orthogonal to both the illumination light axis O′ and a movable direction of the slit plate 24. A projection image of the slit hole 24a to a fundus oculi Er is formed in parallel to a plane including observation light axes of the right and left observation optical systems 30.
The illumination field diaphragm 23 is disposed at a position optically conjugate to an anterior focus position F of the objective lens 15. The slit plate 24 is placed near the illumination field diaphragm 23. The slit hole 24a is formed at a position substantially optically conjugate to the anterior focus position F. The position of the objective lens 15 is adjusted so that the anterior focus position F becomes conjugate to a fundus oculi Er (retina).
The illumination light source 21 may be housed in the lens barrel part 10, or may be disposed outside the lens barrel part 10. In the latter case, illumination light outputted from the illumination light source 21 is guided through an optical fiber to the condenser lens 22 within the lens barrel part 10.
When illumination light is projected to the eye E, the cornea Ec acts as a convex reflection mirror, and part of the illumination light is reflected. When this corneal reflection light enters the observation field (namely, mixes into the fundus oculi reflection light), flare occurs within the observation field and prevents observation.
In the conventional surgical microscope apparatus, the distance between the head lens 13 and the cornea Ec is adjusted manually, thereby preventing corneal reflection light from mixing into fundus oculi reflection light.
Moreover, when the position of the eye E changes, it is necessary to adjust the positions of the optical systems 20, 30 and the head lens 13 in order to observe a target site. This position adjustment is also manually performed by the operator conventionally.
Thus, according to the conventional surgical microscope apparatus, the positional relationship between an eye and a device optical system is manually adjusted, so that there are problems that the concentration of the operator is disturbed, the operation is complicated, and the surgical time is long. Moreover, it is not easy for a not-expert person to manually adjust the positions.